1 /* 2 * SoftDog 0.07: A Software Watchdog Device 3 * 4 * (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved. 5 * http://www.redhat.com 6 * 7 * This program is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU General Public License 9 * as published by the Free Software Foundation; either version 10 * 2 of the License, or (at your option) any later version. 11 * 12 * Neither Alan Cox nor CymruNet Ltd. admit liability nor provide 13 * warranty for any of this software. This material is provided 14 * "AS-IS" and at no charge. 15 * 16 * (c) Copyright 1995 Alan Cox <alan@lxorguk.ukuu.org.uk> 17 * 18 * Software only watchdog driver. Unlike its big brother the WDT501P 19 * driver this won't always recover a failed machine. 20 * 21 * 03/96: Angelo Haritsis <ah@doc.ic.ac.uk> : 22 * Modularised. 23 * Added soft_margin; use upon insmod to change the timer delay. 24 * NB: uses same minor as wdt (WATCHDOG_MINOR); we could use separate 25 * minors. 26 * 27 * 19980911 Alan Cox 28 * Made SMP safe for 2.3.x 29 * 30 * 20011127 Joel Becker (jlbec@evilplan.org> 31 * Added soft_noboot; Allows testing the softdog trigger without 32 * requiring a recompile. 33 * Added WDIOC_GETTIMEOUT and WDIOC_SETTIMOUT. 34 * 35 * 20020530 Joel Becker <joel.becker@oracle.com> 36 * Added Matt Domsch's nowayout module option. 37 */ 38 39 #include <linux/module.h> 40 #include <linux/moduleparam.h> 41 #include <linux/types.h> 42 #include <linux/timer.h> 43 #include <linux/miscdevice.h> 44 #include <linux/watchdog.h> 45 #include <linux/fs.h> 46 #include <linux/notifier.h> 47 #include <linux/reboot.h> 48 #include <linux/init.h> 49 #include <linux/jiffies.h> 50 51 #include <asm/uaccess.h> 52 53 #define PFX "SoftDog: " 54 55 #define TIMER_MARGIN 60 /* Default is 60 seconds */ 56 static int soft_margin = TIMER_MARGIN; /* in seconds */ 57 module_param(soft_margin, int, 0); 58 MODULE_PARM_DESC(soft_margin, "Watchdog soft_margin in seconds. (0<soft_margin<65536, default=" __MODULE_STRING(TIMER_MARGIN) ")"); 59 60 static int nowayout = WATCHDOG_NOWAYOUT; 61 module_param(nowayout, int, 0); 62 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 63 64 #ifdef ONLY_TESTING 65 static int soft_noboot = 1; 66 #else 67 static int soft_noboot = 0; 68 #endif /* ONLY_TESTING */ 69 70 module_param(soft_noboot, int, 0); 71 MODULE_PARM_DESC(soft_noboot, "Softdog action, set to 1 to ignore reboots, 0 to reboot (default depends on ONLY_TESTING)"); 72 73 /* 74 * Our timer 75 */ 76 77 static void watchdog_fire(unsigned long); 78 79 static struct timer_list watchdog_ticktock = 80 TIMER_INITIALIZER(watchdog_fire, 0, 0); 81 static unsigned long driver_open, orphan_timer; 82 static char expect_close; 83 84 85 /* 86 * If the timer expires.. 87 */ 88 89 static void watchdog_fire(unsigned long data) 90 { 91 if (test_and_clear_bit(0, &orphan_timer)) 92 module_put(THIS_MODULE); 93 94 if (soft_noboot) 95 printk(KERN_CRIT PFX "Triggered - Reboot ignored.\n"); 96 else 97 { 98 printk(KERN_CRIT PFX "Initiating system reboot.\n"); 99 emergency_restart(); 100 printk(KERN_CRIT PFX "Reboot didn't ?????\n"); 101 } 102 } 103 104 /* 105 * Softdog operations 106 */ 107 108 static int softdog_keepalive(void) 109 { 110 mod_timer(&watchdog_ticktock, jiffies+(soft_margin*HZ)); 111 return 0; 112 } 113 114 static int softdog_stop(void) 115 { 116 del_timer(&watchdog_ticktock); 117 return 0; 118 } 119 120 static int softdog_set_heartbeat(int t) 121 { 122 if ((t < 0x0001) || (t > 0xFFFF)) 123 return -EINVAL; 124 125 soft_margin = t; 126 return 0; 127 } 128 129 /* 130 * /dev/watchdog handling 131 */ 132 133 static int softdog_open(struct inode *inode, struct file *file) 134 { 135 if (test_and_set_bit(0, &driver_open)) 136 return -EBUSY; 137 if (!test_and_clear_bit(0, &orphan_timer)) 138 __module_get(THIS_MODULE); 139 /* 140 * Activate timer 141 */ 142 softdog_keepalive(); 143 return nonseekable_open(inode, file); 144 } 145 146 static int softdog_release(struct inode *inode, struct file *file) 147 { 148 /* 149 * Shut off the timer. 150 * Lock it in if it's a module and we set nowayout 151 */ 152 if (expect_close == 42) { 153 softdog_stop(); 154 module_put(THIS_MODULE); 155 } else { 156 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n"); 157 set_bit(0, &orphan_timer); 158 softdog_keepalive(); 159 } 160 clear_bit(0, &driver_open); 161 expect_close = 0; 162 return 0; 163 } 164 165 static ssize_t softdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos) 166 { 167 /* 168 * Refresh the timer. 169 */ 170 if(len) { 171 if (!nowayout) { 172 size_t i; 173 174 /* In case it was set long ago */ 175 expect_close = 0; 176 177 for (i = 0; i != len; i++) { 178 char c; 179 180 if (get_user(c, data + i)) 181 return -EFAULT; 182 if (c == 'V') 183 expect_close = 42; 184 } 185 } 186 softdog_keepalive(); 187 } 188 return len; 189 } 190 191 static int softdog_ioctl(struct inode *inode, struct file *file, 192 unsigned int cmd, unsigned long arg) 193 { 194 void __user *argp = (void __user *)arg; 195 int __user *p = argp; 196 int new_margin; 197 static struct watchdog_info ident = { 198 .options = WDIOF_SETTIMEOUT | 199 WDIOF_KEEPALIVEPING | 200 WDIOF_MAGICCLOSE, 201 .firmware_version = 0, 202 .identity = "Software Watchdog", 203 }; 204 switch (cmd) { 205 default: 206 return -ENOTTY; 207 case WDIOC_GETSUPPORT: 208 return copy_to_user(argp, &ident, 209 sizeof(ident)) ? -EFAULT : 0; 210 case WDIOC_GETSTATUS: 211 case WDIOC_GETBOOTSTATUS: 212 return put_user(0, p); 213 case WDIOC_KEEPALIVE: 214 softdog_keepalive(); 215 return 0; 216 case WDIOC_SETTIMEOUT: 217 if (get_user(new_margin, p)) 218 return -EFAULT; 219 if (softdog_set_heartbeat(new_margin)) 220 return -EINVAL; 221 softdog_keepalive(); 222 /* Fall */ 223 case WDIOC_GETTIMEOUT: 224 return put_user(soft_margin, p); 225 } 226 } 227 228 /* 229 * Notifier for system down 230 */ 231 232 static int softdog_notify_sys(struct notifier_block *this, unsigned long code, 233 void *unused) 234 { 235 if(code==SYS_DOWN || code==SYS_HALT) { 236 /* Turn the WDT off */ 237 softdog_stop(); 238 } 239 return NOTIFY_DONE; 240 } 241 242 /* 243 * Kernel Interfaces 244 */ 245 246 static const struct file_operations softdog_fops = { 247 .owner = THIS_MODULE, 248 .llseek = no_llseek, 249 .write = softdog_write, 250 .ioctl = softdog_ioctl, 251 .open = softdog_open, 252 .release = softdog_release, 253 }; 254 255 static struct miscdevice softdog_miscdev = { 256 .minor = WATCHDOG_MINOR, 257 .name = "watchdog", 258 .fops = &softdog_fops, 259 }; 260 261 static struct notifier_block softdog_notifier = { 262 .notifier_call = softdog_notify_sys, 263 }; 264 265 static char banner[] __initdata = KERN_INFO "Software Watchdog Timer: 0.07 initialized. soft_noboot=%d soft_margin=%d sec (nowayout= %d)\n"; 266 267 static int __init watchdog_init(void) 268 { 269 int ret; 270 271 /* Check that the soft_margin value is within it's range ; if not reset to the default */ 272 if (softdog_set_heartbeat(soft_margin)) { 273 softdog_set_heartbeat(TIMER_MARGIN); 274 printk(KERN_INFO PFX "soft_margin value must be 0<soft_margin<65536, using %d\n", 275 TIMER_MARGIN); 276 } 277 278 ret = register_reboot_notifier(&softdog_notifier); 279 if (ret) { 280 printk (KERN_ERR PFX "cannot register reboot notifier (err=%d)\n", 281 ret); 282 return ret; 283 } 284 285 ret = misc_register(&softdog_miscdev); 286 if (ret) { 287 printk (KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n", 288 WATCHDOG_MINOR, ret); 289 unregister_reboot_notifier(&softdog_notifier); 290 return ret; 291 } 292 293 printk(banner, soft_noboot, soft_margin, nowayout); 294 295 return 0; 296 } 297 298 static void __exit watchdog_exit(void) 299 { 300 misc_deregister(&softdog_miscdev); 301 unregister_reboot_notifier(&softdog_notifier); 302 } 303 304 module_init(watchdog_init); 305 module_exit(watchdog_exit); 306 307 MODULE_AUTHOR("Alan Cox"); 308 MODULE_DESCRIPTION("Software Watchdog Device Driver"); 309 MODULE_LICENSE("GPL"); 310 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR); 311